name two things that occur when the kinetic energy of incident electrons increases:

an increase in quantity and quality

an increase in the number of target interactions

how do electrons dissipate excess energy involved in x-ray production?

they can undergo 1000+ interactions (energy never disappears)

over how much area do target interactions occur?

within .25 to .5 mm of target surface

name three things that occur on the target surface during x-ray production:

heat production

bremsstrahlung interactions

characteristic interactions

what percent of the incident electrons' kinetic energy is converted into heat?

99%

where do incident electrons transfer kinetic energy to?

outer shell electrons of the target atoms

(causes them to emit infrared radiation, or heat)

what are the two most common target materials and why?

tungsten and rhenium

because of their high melting points and high atomic numbers

name the atomic number and melting point of both tungsten and rhenium:

tungsten (W): 74Z#, 3370°C

rhenium (Ru): 44Z#, 3170°C

what is the most common target material used in mammography and why?

molybdenum

its lower atomic number is helpful due to the lower energies needed in mammography

name the atomic number of molybdenum:

molybdenum (Mo): 42Z#

define Bremsstrahlung:

german origin, meaning "breaking" or slow down

in discussing Bremsstrahlung, what does the incident electron interact with?

the electrostatic force field of the nucleus

in discussing Bremsstrahlung, what occurs with the presence of a strong nuclear force?

the force keeps the incident electron and the nucleus apart and deflects the incident electron

in discussing Bremsstrahlung, describe the result of a nucleus with a high atomic number and an incident electron with low energy:

the incident electron doesn't penetrate the electrostatic force field to reach the nucleus

name what is occuring in the following diagram and compare incident electron A to incident electron B:

bremsstrahlung x-ray production is occuring.

electron B has more energy than electron A. therefore, it passes closer to the nucleus, makes a greater curve or change in direction at the nucleus, and produces a higher energy bremsstrahlung x-ray photon compared to electron A

it is important to note that ____________ does not occur with bremsstrahlung interactions.

ionization

if an incident electron has 40kEv as it approaches the nucleus, and it has 20kEv as it leaves the nucleus, how much bremsstrahlung energy has occurred?

20kEv

Brems interactions account for what percent of the x-ray beam?

85-100%

in dealing with tungsten, what is the kEv needed to make characteristic x-ray?

69kEv

what two things occur as incident electrons get closer to the nucleus?

photon energy increases

larger deflection of the incident electron

describe what we know about direct interaction between the nucleus and the incident electron:

this would be the maximum energy photon, and though possible, it is highly improbable

what do incident electrons interact with?

the k-shell electron

(then the incident electron continues in a slightly different direction)

in a characteristic interaction, the __________ energy must overcome the ___________ energy.

kinetic

binding

(occurs in techniques using 70kVp or higher)

describe/explain what is occurring in a characteristic cascade:

there is a "hole" in an inner shell, and it must be filled by an electron from an outer shell. this creates an electron energy difference and secondary photons are produced.

only electrons that drop into _____________ will contribute to the beam.

the k-shell

describe how to find the brems energy if you know the binding energies of electron shells, give an example:

subtract the binding energy of the more outer shell from the binding energy of the more inner shell to find the brems energy that will result:

Ex: if a K shell is 40kEv, the L shell is15kEv, then the brems energy will be 25kEv (40-15=25)

name the graph:

kVp emission spectrum chart

this is on tungsten, you can tell because characteristic peaks are occurring at 69keV

compare average kVp to selected kVp:

average is approximately 30-40% of the selected

ex. 90kVp will produce an average of 30keV

name the graph:

mA chart

denotes a change in mA, time, or mAs

changes the beam amplitude

in the emission spectrum, what happens when there is a change in kVp?

changes in beam amplitude and average energy

(due to an increase in the kinetic energy provided to incident electrons)

NO increase in electrons striking the target

in a kVp emission spectrum chart, why does the number of xray photons increase on the chart as the keV increases?

there are the same number of electrons, but there are more interactions

name the graph:

chart showing the emission spectrum with a change in generators (single phase to three phase)

overall ave energy of single phase is 25keV

overall ave energy of three phase is 30-35keV

the top of the hump is the amplitude

what is attenuation?

reduction in the number of x-ray photons in the beam as it passes through matter

what atomic parts do x-rays typically interact with (attenuation)?

entire atom

orbital electron

neucleus of an atom

when an x-ray interacts with the entire atom, this is a:

coherent interaction

an interaction in which an electron is ejected from an atom results in _____________ and occurs with which types of interactions?